Telephone system



Patented Oct 11, 1932 unites stares eeann rarer errsiea NORMAN H. SAUNDERS, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, l TO ASSOCIATED ELECTRIC LABORATORIES, INC., OF CHICAGO, ILLINOIS, A COBPORA- TION OF DELAWARE rnnnrnonn sYs'rEn Application filed September 30,1931. Serial No. 566,083.

This invention relates to telephone systems in general, particularly to systems in which commonswitching apparatus is employedin the'establishment oficonnections, and is concerned primarily with arrangements for preventing the unnecessary occupation of such apparatus by defective lines.

Arrangements for preventing defective lines from holding commorr switching apparatus out of service are shown in the copending application of J. A. Burgener, Serial No. 455,541, filed May 26, 1930, and in applicants Patent No. 1,834,649, granted Dec. 1, 1931, on which the present invention maybe considered. an improvement. In the prior systems, the equipment provided for locking out defective lines has been associated individually with the various lines. The greater part of this equipment will normally be idle as-ordinarily only a relatively small number of thelines in a telephone system will be defective at any one time. It is the main object of the present invention to produce a lockout arrangement for use under theabove conditions, which will be more efficient and economical than the prior arrangements This object is attained by making the lockout equipment commonto a number of lines thereby greatly reducing the amount of such equipment necessary tocare for the normal requirements of a telephone system,

The various features of the invention together with the operation of the equipment 1n a telephone system embodying the same, will be describedin detail hereinafter, reference being had to the accompanying single figure of drawing. The embodiment'ofthe invention in an automatic telephone system has been shown in the drawing by wayof illustration. Itwill be understood, however, that the invention is not limitedto use in such systems but may be applied equally well to semi-automatic and manual systems as will be readily apparent to those skilled in the v The drawing shows only sufficient of the equipment of a telephone exchange necessary for;'a clear understanding of-the invention. T represents an-ordinaryautomatic substation-telephoneset. -LS is arotary, primary lineswitch of the well known type terminating the line from the substation T. COR is a group of cut-off relays associated with a pair of trunk. lines accessible .to the-lineswitch LS, and S isa Strowger type selector switch of which only the line andrelease relays have been shown. It will'be notedthat the pair.

of trunk lines accessible in the first and ninth bank positions "of the lineswitch extend to the out-01f relay group and from this point-a single four-conductor trunk extends to the selector. The circuit of the selector .9) has been modified slightly by the provision of an additional set of contacts forthe release relay system, for example, intervals of two minutes will permit the holding of the selector for a minimum of two minutes or a maxi- The particular interval/chosen will mum of four minutes before-the lockout equipment functions. f V i Proceeding now with the detailed description, it will first be assumed that the subscriber at substation T initiates a call and which thewipers of the lineswitch is'stand ing at this time is in use, wiper 16 will find ground on the test oontact,which is extended over a circuit including contacts 11,. 7 ,and'

14, to energize stepping magnet -e,'and shunt j relay 5. The stepping magnet operates and interrupts its own circuit atcontactsi14 and.

on restoring advancesthe wipers one step. .Th1s operation is repeated'aslong as WIPGI" 16 encounters grounded contacts. When an idle trunk is found the absenceof ground" V the line relay is opened at contacts 9 and 13 and the test wiper is connected to the upper terminal of relay 5 at contacts 30. Assuming that the selected trunk is the one comprising conductors 1820, an operating circuit can now be traced for relay 51 of the selector S, from battery through the upper winding of the relay, conductor 21, contacts 34, wiper15, contacts 10, line conductor 1, through the loop at the calling substation, line conductor 2, contacts 12, wiper 17 conductor 20, contacts 43, conductor 23, lower winding of relay 51 to ground. Relay51 operates and completesa circuit for relay52 at contacts 53. Relay 52 operates, prepares the timing circuit at contacts 55, prepares the impulsing circuit at contactsi56, and at. contacts 58 applies ground to release trunk conductor 48 which extends. back. by way of contacts 39, conductor 19, wiper 16 and contacts 30 to relay 5. Switching relay 5 of the lineswitch is held operated over. this circuit after slow-releasing relay 4-restores which occurs a short time after its circuit is opened by the operation of relay 5.

In'case the calling subscriber dialsbefore the interrupter appliesground to conductor 60, the selector will he stepped ofi-normal in the usual way, thereby interrupting the timing. circuitat off-normal contacts 59. ,Accordingly, when the interrupter applies ground to the'conductor 60 no operation of the lockout equipment will take place and the call will be extendedthrough succeeding switches in the usual manner responsive to 7 further dialling.

' tor 47, contacts 44, upper winding ofxtwostep relay 32 to battery. Relay32 willoperate in its first step in which position contacts 46 are closed'as indicated by the Roman numeral I, while the remaining contacts designated by the Roman numeral 11 remain in their normal positions, Ground is vremoved from conductor 60. after a short interval by the continued operation of the interrupter, thereby permitting relay 32 to opera-tetfully overa circu t including its two windings in series, contacts 46 and groundedconductor48; Relay 32' opens itsinitial en-L erg'izing circuit at contacts 44 and extends. conductor 47 through tothe upper winding of relay 31 byway of contacts 45 In case i g the calling subscribernoxt dials, theselector will be stepped off-normal in the usual way and the timing circuit will beinterrupted at contacts 59. The call will be further extended in the usual manner and no further operation takes place at the cut-oil relay group, although relay 32 will remain energized until'the connection is released and ground is removed from release trunk conductor 48-to which the relay remains locked.

In the event that a line becomes short-circuited or grounded, or in case a subscriber removes his receiver without dialling within a reasonable time, in the manner previously described, relay 32 will operate on the first "application of ground to the timing circuit ground to conductor 20 at contacts 42. The

relaywill remain operated over this circuit aslong as the short-circuit remains on the line. The trunk comprising conductors 21- 23 which is accessible in the ninth position of the lineswitch LS will be separated from the trunk comprising conductors 182O accessible in the first position of the lineswitch LS by the opening of contacts 34, 39, and 43. The busying ground will be removed from test conductor 22 of the ninth position trunk bythe opening of contacts 41 and this con:

ductor willbe connected through to release trunk conductor 48 at contacts 40. Ground will now be applied to test conductor 19 of the. first position trunk at contacts 38 to hold up the switching relay of the lineswitch LS until the line is cleared. We now have the condition of the lineswitch having seized the first position trunk and being looked over this trunk while the tenth position trunk is now made accessible to otherlineswitches and is connected through" to selector S. The supervisory lamp L will glow as a circuit is closed at contacts 33, thereby notifying the exchange attendant that a line is locked out due to trouble,

In case the trouble is cleared from the line while the ninth position trunk is idle, the holding circuit for relay31 will be opened and that relay willrestore, thereby returning the trunk to normal condition, that is, with the first position trunk accessible to lineswitches andthe ninth position trunk marked busied-by ground at'contacts 41; However,

if another call is in progress on the ninthv positiontrunk at the time the first position trunk iscleared, relay -31 willbeheld operatedfrem ground on release trunk conductor48, contacts 4Q'and 37, lower winding of relay 31 to b attery. The first position trunk will accordingly be busied and when the con- 'nection over. the ninth position trunk is fina-l ly released and ground is removed from the release'trunk conductor, relay 31 will restore and permit the release of the lineswitch over which the first position trunk was originally seized. r

In case the connection ext-ended over the ninth position trunk is one from a shortcircuited line the selector will be held out of service as no provision is made for the lockoutof such connections. .This,.however, will ordinarily be a rare occurrence since the number of lines which are defective at any one time in a system are usually few in number.

What is claimed is 1. In a telephone systemya line, first switchterminating said line, a second switch terminating a trunk accessible to said first switch, means controlled over the line for operating said firstswitch to connect the line with said second switch via said trunk, and

means revertively controlled from said second switch over said trunk for disconnecting the line from said second switch without releasing saidfirst switch. a i i 2. In a telephone system, a line, a first switch terminating said line, a second switch accessible'to said first switch, means responsive to a condition placed on said line for operating said first switch to connect the line with said second switch, and means for disconnecting the line from said second switch andfor maintaining said first switch in operated position until said condition'is removed from the line. 7

3. In a telephone system, a line, a first switch, asecond switch, means responsive to particular condition placed on the line for operating said first switch to connectthe line with said second switch, and means interposed between said two switches for freeing said second switch from the connection and for maintaining said first switch operated as long as said particular condition exists on the line.

4:. In a telephone system, a line, a first and second switch, means responsive to a condition placed on said line for operating the first switch to connect the line to the second switch, a timing device, and means controlled bythe timing device for freeing said second switch from the connection and for m IIItEIlH ing said first switch operated'as long as said condition exists on the line.

5. In atelephone system, a line, a first and second switch, means responsive to the initiation of a call on said line for operating the first switch to connect the line to the second switch, means in the second switch directively controlled over the line for setting the second switch, and means automatically operated re I standard condition on the line for operating the first switch to connect the line to the secondswltch, and means automatically operated a predetermined time after the establishment of the connection for freeing the associated individual switch to connect the line to saidtsecond switch, means for preventing'the connection'of another line to saidsecond switch while said connectionis maintained, and means for disabling-said connection preventing means and for maintainingsaid first switchjoperated as longas said condition exists on said one line.

- 8. In a telephone system, a plurality of lines, aswitching device accessible to said lines in common,means for connecting any one of sa1d lines to sa1d device, means for lpreventinga second connection to-the-devic-e v while oneconnection exists, lockout means assoclated wlth said device, means for asso- .ciating said lockout means individually with any one of the lines connected to said device, and means controlled by said lockout means for freeing said device for connection with other lines while saidlockout means remains associated with said one line. H v

:9. In a telephone system, a plurality of lines, a switching device common to said lines, means for connecting any one of said lines to said device, a relay adapted to be connected to any one of said lines which may be connected to said device, means for operating said relay, and means controlled by said relay for disconnecting said oneline from the device and for maintaining itself operated over the line.

10. In a telephone system,aplurality-of vlines,ea switching device accessible .to said lines, IIIBELIIS'IGSPOIISlVB to a condition placed on any one of said lines for connecting the line to sa1d device, means responsive-to sa1d connection for rendering the device inaccessible to the remaining l1nes,a lockout relay common to said lines, contactscontrolled by said relay for interrupting the connectlon between a line and said device and for renlines, and means controlled by'said device for initiating the onerationof said relay.

dering the device accessible toithe remaining 11. In,a;teleph one system, a plurality of lines each terminating in an automatic Pal switch, contact banks forfi li'dswitches, a trunkiline connected to two, dlfiGIfllhPOSb tionsl' of said banks andv normally accessible in only one posit on, means responsiveto a particular condition on any one of said lines for operating the associated switch to connect with said trunk via said one position, and means for disconnecting the trunk line from said one bank position and for rendering the same accessible to the remaining ones 4 of said switches in the other bank position.

12. In a telephone system, a trunk line normally accessible in a particular position in the ba-nksof a group otfree hunting automatic switches, and means automatically one path and accessible over a different path,

and means controlled over the trunk line for rendering the trunk line inaccessible over said diiierent path and for maintaining the trunk line inaccessible over said one path when a connection is extended to the trunk line over said difierent pathk,

14. The combination with a trunk line having two branches, of means normally eiiective to mark one of the branches busy, and means for removing the busy condition from said one branch and for disconnecting the other branch from the trunk line.

15. In a telephone system, a switching de- Vice, a trunk line terminating in said device, two branches for the trunk line, means for extending a connection to said device via the trunk line and one branch, and means I the lineswitches, a trunk line, two separate .line. i 17. In a telephone system, a group of lines,

ing two normally connected branches, of means for marklng one of said branchesbusy,

means for removing'the busy condition from said one branch and for disconnecting the other branch from the trunk line, and means controlled over said other branch for maintaining the last said condition of the'trunk a lineswitch for each line,contact'banks for sets of 'contacts'in each of said banks for the trunk line, and means responsive to the seizure of the trunk line via one of said contact sets and the lineswitch of a line on which an unstandard condition exists for making the trunk line accessible to the remaining lineswitches over sets.

18. In a telephone system,a group of lines, a lineswitch for each line, contact banks for the lineswitches, a trunk line,a plurality of separate sets of multiplied' contacts in said theother of said contact a certain condition. on one. of said lines for operating the/associated lineswitch to connect with said trunk line over one set of contacts, and a time controlled device for dis-. connecting said one set of contacts from the trunk line and for .making the trunk line accessible to the remaining lineswitches over a diiierent set of contacts.

19. Ina telephone system, a group of lines, a switch for eachline, contact banks for the switches,-a trunk line, a first contact set and a second contact set in each of said banks for the trunk line, multiple connections between said first contact sets, multiple connections between said second contact sets, means responsiveto the occurrence of certain conditions on one of said lines for operating the associated switch to connect with the-trunk line via the first of said contact sets in its bank, means responsive to the establishment nection of another switch tothe first of said contact sets in its bank, and means for making the trunk line accessible to the remaining switches over the second contact sets in their respective banks while said one switch remains connected to said first contact set. 20. The combination with a trunk line having two branches, of means normally efiect1ve formaking one of said branches inaccessible, meansfor extending connections from lines to the trunk line via the other of said branches, means operative when such connection is extended from' a'line on which an unstandard condition exists for disconnecting said other branch from the trunk line without disconnecting the line from that branch and for disabling the first said means. In witness whereof, I hereunto subscribe myvname this 24th day of September, A. D.

. NORMAN SAUNDERS.

ofsaid connection for preventing the conbanks for the trunk line, means responsive to .i 

